1. Field of the Invention
The present invention relates generally to antenna systems for radiating wave energy beams and more particularly to antenna systems which radiate a plurality of orthogonal beams.
2. Description of the Prior Art
It is well known that most any desired wave energy pattern may be approximately achieved using a combination of component antenna beams which result from component aperture excitations. The desired wave energy pattern results from the superposition of the component beams in space, and a corresponding composite aperture excitation is determined by the superposition of the component aperture excitations.
In practice, it is convenient to choose component aperture excitations which radiate an orthogonal set of component beams. In a conventional orthogonal set of antenna beams, each beam has a direction of maximum radiation associated with it, in which direction all other beams in the orthogonal set exhibit a radiation null. Using an orthogonal set of component antenna beams results in there being a corresponding set of directions in space at each of which the amplitude of radiation is predominantly determined by the amplitude of a single component aperture excitation.
In order to radiate multiple overlapping beams, most prior art radar systems have found that channel separation was a necessity. In particular, such prior art systems were forced to employ duplexers, filters, and switches in order to achieve the desired channel separation. These systems tacitly assume that orthogonality requires displacing the beams in angle.